The mouse antibody heavy chain complex locus will be analyzed by genetic crosses using V gene markers to determine the number of structural genes, their organization, and their linkage relationships with neighboring genes. Their location in the genome will be discovered by analysis of Recombinant Inbred strains. This knowledge will reveal mechanisms involved in antibody expression and regulation such as V-C translocation and allelic exclusion. Light chain structural genes will be identified and used in similar genetic analysis to determine if the same mechanisms are used at these loci and to compare the relative sizes of the light chain and heavy chain V gene libraries. The generation of antibody diversity will be studied by comparing the amino acid sequences of lambda light chains from a series of monoclonal antidextran antibodies.